I assumed, given he died aged 64 and that the Legion of Frontiersmen was the only contingent allowed to enlist men over age, that Frederick Courtney Selous was the oldest soldier to die in WW1 when he was shot by a sniper at BehoBeho on 4 January 1917.
A visit to the Temple Church in London taught me, once again, not to assume! In their World War 1 exhibition they named had a soldier who I recalled was 65 when he died. My photographic skills having failed me, I couldn’t work out his name when I came to do this write-up, so a quick search (I assumed) on the WWW for his name revealed he wasn’t the oldest soldier to have died in the war either! According to the BBC and the Telegraph, it was a 67 year old man from Tonbridge, Henry Webber. The Great War Forum provides some other little interesting snippets about the oldest who died and is worth a quick skim through.
For those of you wondering who the Temple man was, thanks to John at Temple Church, who kindly went to check for me, he was Jasper Myers Richardson of the Inner Temple who died aged 68 (! not 65 as I initially thought). And, yes, he was in fact (so far as is currently known) the oldest British man to die on active service during WW1.
Another assumption which needs to be corrected is that FC Selous of the 25th Royal Fusiliers (Legion of Frontiersmen) was not the only man to die on 4 January at BehoBeho. A sad follow-on to Selous’ death was that of his son, Frederick Hatherley Bruce, who died exactly a year to the day on 4 January 1918 on the Western Front.